1. Field of the Invention
The present invention is broadly concerned with methods of forming antireflective coating (ARC) layers on silicon and dielectric materials as well as the resulting integrated circuit precursor structures. More particularly, the inventive methods comprise providing a quantity of a highly strained antireflective compound and vaporizing that compound. The resulting vapor is then pyrolized to form stable diradicals which are subsequently polymerized on the surface of a substrate. A photoresist layer is applied to the formed ARC layer, and the remaining microphotolithographic process steps carried out.
2. Description of the Prior Art
Integrated circuit manufacturers are constantly seeking to maximize silicon wafer size and minimize device feature dimensions in order to improve yield, reduce unit case, and increase on-chip computing power. Device feature sizes on silicon chips are now submicron in size with the advent of advanced deep ultraviolet (DUV) microlithographic processes. However, reducing the substrate reflectivity to less than 1% during photoresist exposure is critical for maintaining dimension control of these submicron features. Therefore, light absorbing organic polymers are formed into antireflective coating (ARC) compositions which are applied beneath photoresist layer in order to reduce the reflectivity normally encountered from the semiconductor substrates during the photoresist DUV exposure. These organic ARCs are typically applied to the semiconductor substrates by a process called spincoating. While spincoated ARC layers offer excellent reflectivity control, their performance is limited by their nonuniformity, defectivity and conformality constrictions, and other inefficiencies inherent within the spincoating process. As the industry approaches adoption of eight-inch or even twelve-inch semiconductor substrates, the inherent inefficiencies of the spincoating process will become increasingly magnified.
Another problem with the current ARC application processes is inadequate coating uniformity across the wafer. The formed layers are typically lacking in uniformity in that the thickness of the layer at the edges thereof is greater than the thickness at the center of the substrate.
Spincoated ARC layers also tend to planarize or unevenly coat surface topography rather than form highly conformal layers (i.e., layers which evenly coat each aspect of the substrate and the features). For example, if an ARC with a nominal layer thickness of 1000 Å is spincoated over raised features having feature heights of 0.25 microns, the layer may prove to be only 350 Å thick on top of the features, while being as thick as 1800 Å in the troughs located between the raised features.
When planarization occurs with these ultra microscopic feature sizes, the ARC layer is too thin on the top of the features to provide the desired reflection control at the features. At the same time, the layer is too thick in the troughs to permit efficient layer removal during subsequent plasma etch. That is, in the process of clearing the ARC deposit from the troughs by plasma etch, the sidewalls of the resist features become eroded, producing microscopically-sized, but significant, changes in the feature shape and/or dimensions. Furthermore the resist thickness and edge acuity may be lost, which can lead to inconsistent images or feature patterns as the resist pattern is transferred into the substrate during subsequent etching procedures.
Other problems can occur as well due to the fact that spincoating of these ultra thin ARC layers takes place at very high speeds in a dynamic environment. Accordingly, pinholes, voids, striations, bubbles, localized poor adhesion, center-to-edge thickness variations, and other defects occur as a consequence of attendant rapid or non-uniform solvent evaporation, dynamic surface tension, and liquid-wavefront interaction with surface topography. The defects stemming therefrom become unacceptable with increased wafer size (e.g., 8″-12″) and when patterning super submicron (0.25 μm or smaller) features.
There is a need for an improved process of depositing ARC on various substrates which overcomes the drawbacks inherent in spincoating.